Vassal adjectives are listed in this post. Each word below can often be found in front of the noun vassal in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing VASSAL.
faithful, feudal, great
humble, loyal, mere
new, obedient, own
powerful, rebellious, silly
Hope this word list had the adjective used with vassal you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.
Please add more adjectives to make this list more complete: